1. Field of the Invention
The invention relates to compressors, and more particularly to compressors of the type used for turbocharging engines, where the turbocharger includes an internal recirculation valve.
2. Description of Related Art
Turbochargers have been used for many years for enhancing the performance of engines used in vehicles, such as automobiles, pick-up trucks, sport utility vehicles, and tractors.
As shown in FIG. 1, such turbochargers 10 typically include a turbine 12 driven by exhaust gas from the engine 14, and a compressor 16 driven by the turbine 12 of the turbocharger 10. The compressor 16 has an inlet 18 for ingesting air at atmospheric pressure, and an outlet 20 connected to an engine air intake 22 for providing a flow of pressurized air to the engine 14.
During certain operations, such as shifting gears in a transmission attached to the engine, when the vehicle operator releases pressure on the accelerator pedal of the vehicle, the compressor becomes unloaded, and can experience undesirable forces on blades of the compressor that could lead to premature failure of the compressor. To address this potential problem, turbochargers often include an internal recirculation valve 24 that is actuated, when needed, to provide an internal recirculation path, through the recirculation valve 24, connecting the outlet 20 of the compressor 16 back to the inlet 18 of the compressor. The recirculation is done internally to reduce the generation of sounds, during recirculation, which might be objectionable to the vehicle operator.
FIG. 2 shows one commonly used type of internal recirculation valve 24. The valve 24, shown in FIGS. 2–3, includes a housing 26 having a lower edge (as shown in FIG. 2) adapted for bolted attachment to a valve mounting flange 28, with three screws 27. The valve mounting flange 28 includes a generally planar face 30, thereof, and defines a recirculation valve inlet port 32 and a recirculation valve outlet port 34. The recirculation valve inlet port 32 is operatively connected in fluid communication with the compressor outlet 20, and the recirculation valve outlet port 34 is operatively connected in fluid communication to the compressor inlet 18. A gasket (not shown) may be used for sealing the juncture between the housing 26 of the recirculation valve 24 and the face 30 of the valve mounting flange 28.
FIG. 3 is a schematic cross-sectional representation of the interior of the recirculation valve 24, with the valve 24 mounted on the mounting flange 28. The housing 26 of the recirculation valve 24, and a movable diaphragm 36 define an internal fluid cavity 38, having an inlet/outlet 40 adapted for connection to a source of vacuum and air pressure. The diaphragm 36 includes a poppet 42, often fabricated from plastic, centered over the compressor outlet port 34 of the valve mounting flange 28, for blocking a flow of pressurized air through the recirculation valve 24 into the recirculation valve outlet port 34, when the diaphragm 36 is positioned such that the poppet 42 is seated against the face 30 of the mounting flange 28. The recirculation valve also includes a compression spring 44 for biasing the poppet 42 toward contact with the mounting flange 28.
When the recirculation valve 24 is operating in a recirculation mode, a vacuum is applied to the inlet/outlet 40, to pull the diaphragm 36 and poppet 42 away from the face 30 of the mounting flange 28, to thereby provide a fluid connection between the recirculation valve inlet and the outlet 32, 34 of the mounting flange 28, and allow recirculation of air through the recirculation valve 24 from the compressor outlet 20 to the compressor inlet 18.
When the recirculation valve is operated in a non-recirculation mode, pressurized air is applied to the inlet/outlet 40, to aid the spring 44 in holding the diaphragm 36 and poppet 42 against the surface 30 of the mounting flange 28, to thereby block recirculation through the recirculation valve 24.
Although recirculation is normally carried out internally to the recirculation valve 24, as described above, to reduce the generation of sounds during recirculation, which might be objectionable to the vehicle operator, there are those who desire to have the recirculation valve outlet 34 vent externally, when the recirculation valve is operating in the recirculation mode, to generate a desired sound, such as a whine, instead of having internal recirculation. In the past, aftermarket manufacturers have sold kits including a venting valve that replaces the original equipment manufacturers (OEM) recirculation valve, together with such altered compressor air manifolds and controls for the venting valve as may be required for operation of the venting valve. Such kits are relatively expensive, and may require replacement of the OEM parts, and altering operation in a manner that adversely affects operation and life of the turbocharger.
It is desirable, therefore, to provide an improved apparatus and method for providing external venting of a turbocharger compressor having an internal recirculation valve, or converting an existing internal recirculation valve on a turbocharger to vent externally. It is highly desirable that such an improved apparatus and method be provided in a manner requiring minimal modification of the OEM turbocharger, the recirculation valve, associated controls and air ducting, and in a manner that can be implemented at a lower cost than prior approaches to providing external venting of the turbocharger compressor.